1. Field of the Invention
This invention relates to a communication system, a communication apparatus, and a communication control method preferably used particularly with various monitoring systems requiring continuous monitoring for many hours.
2. Description of the Related Art
In recent years, development of open wireless communication systems, such as a radio LAN and Bluetooth (registered trademark), has been brisk. In the communication systems, fully wireless slaves are provided.
However, the communication systems assume that the use time of a slave at a time is short (about several hours); while the slave is used, it consumes power of about 10 mA if the slave is not in communications. Therefore, the communication systems are not fitted for applications where the slave is used continuously for along time, for example, the monitoring system field requiring long-hour monitoring.
On the other hand, a radio communication system for a monitoring system has been provided as an individual system (closed wireless communication system). Some attempt has been made to provide a fully wireless slave, but power consumption causes a bottle neck in realizing a fully wireless slave; a system is only realized wherein the communication start direction is one way, namely, only a communication start request sent from a slave to a master is enabled.
However, to advance the function of a monitoring system in the future, it will become very important to make it possible to establish communications between a slave and a master when either the slave or the master makes a communication start request at any time. That is, the system wherein only a communication start request in one way is enabled as described above will block advancing the function of a monitoring system in the future; this is a problem.